As is well appreciated in the art, there are myriad technological obstacles in the identification, enumeration, detection, capture, and isolation of rare cells. These technological obstacles tend to limit the quantitative evaluation of rare cells, for example, in early diagnosis of metastatic diseases and effective monitoring of therapeutic response in patients.
Some rare cells, e.g. circulating tumor cells (CTCs) and/or viable tumor-derived epithelial cells, are identified in peripheral blood from cancer patients and are likely the origin of intractable metastatic disease. CTCs, as just one type of rare cell, tend to be present in an amount of about 1 CTC per 1 billion blood cells and tend to circulate in peripheral blood of patients with metastatic cancer. Detection, isolation, and capture of CTCs represent a potential alternative to invasive biopsies during diagnosis of disease. More specifically, the ability to identify, isolate, propagate and molecularly characterize CTC subpopulations could further the discovery of cancer stem cell biomarkers, expand the understanding of the biology of metastasis, and improve the therapeutic treatment of cancer patients and the ultimate treatment outcome. Many current strategies for isolating CTCs are limited to complex analytic approaches that are typically very low yield and/or low purity.
Many existing technologies for capturing CTCs utilize size based separation techniques. For example, CTCs derived from solid tumors tend to be larger in size compared to typical red blood cells. For this reason, techniques have emerged wherein CTCs are passed through pores etched in membranes wherein the CTCs are trapped on the membrane. However, these techniques tend to suffer from clogging of the pores and pressure drops in devices that include such membranes due to collection of cells on the membranes. In addition, the viscoelastic properties of CTCs allow such cells to squeeze, or be pushed, through the pores. For this reason, related techniques have resorted to pre-fixation of the cells. However, one of the major limitations associated with pre-fixation is adequate throughput and excessive non-specific cell retention. Although processing speeds of such methods tend to be efficient compared to immunoaffinity capture based methods, the amounts of samples that can be processed without sacrificing efficiency and purity is limited. Accordingly, there remains an opportunity to develop an improved method and device for detecting rare cells.
This disclosure provides a microfluidic device for detecting rare cells in a fluid sample that includes the rare cell and other cells. The microfluidic device comprises an inlet for receiving the fluid sample, a labyrinth channel structure in fluid communication with the inlet, and an outlet in fluid communication with the labyrinth channel structure for collecting the rare cells separated from the other cells in the fluid sample. The labyrinth channel structure comprises at least one channel through which the fluid sample flows. The at least one channel has a plurality of segments and a plurality of corners with each corner defined between adjacent segments. The presence of the plurality of corners induces separation of the rare cells from the other cells in the fluid sample as the rare cells move to a first equilibrium position within the at least one channel when a ratio of inertial lift forces (Fz) and Dean flow (FD) of the fluid sample is from 2 to 10.
A method for detecting rare cells is also disclosed herein. The method comprises providing a microfluidic device comprising an inlet, a labyrinth channel structure in fluid communication with the inlet and comprising at least one channel having a plurality of segments and a plurality of corners with each corner defined between adjacent segments, and an outlet in fluid communication with the at least one channel. The method further comprises introducing the fluid sample into the inlet of the microfluidic device, flowing the fluid sample through the labyrinth channel structure, and separating the rare cells from the other cells in the fluid sample as the fluid sample flows past the plurality of corners in the at least one channel of the labyrinth channel structure. The rare cells move to a first equilibrium position within the at least one channel when a ratio of inertial lift forces (Fz) and Dean flow (FD) of the fluid sample is from 2 to 10.